A Kuwaiti family has won the lawsuit which was filed in London against the Credit Suisse Group AG after the family lost worth $29 million of investments with the bank during the 2008 financial crisis. Mahmoud Haji Haider Abdullah and his sons, Maytham, Mahdi, and Mansour, had lost $29 million at the end of October 2008, Judge Andrew Baker said Monday, without defining how much money they can recover.

Filings in the case say the family is worth at least half a billion dollars. He said the bank was responsible for “actionable breaches of duty” over the family’s purchase of a $20 million three-year note in May 2008. In October 2008, Maytham and Mahdi chose not to meet a margin call issued by Credit Suisse, which meant they suffered “a total loss of their net investment” in a series of notes and were left overdrawn at Credit Suisse by $336,275.60.

The bank had argued that the family’s refusal to meet the margin call “was so unreasonable as to amount to a failure to mitigate loss,” and that the losses “resulted from the extreme nature and severity of the 200 crash,” the judgment read. But the judge said, “it was not unreasonable to prefer to exit their investments and stop their losses as they did.”

A spokesman for the bank declined to comment, and lawyers for the family didn’t want to immediately comment. Baker didn’t say how much the bank should pay the family. He said one method would put the figure at $17.9 million, and he wanted further calculations to be done before determining the final amount.

He said the Kuwaiti family, who were clients of Credit Suisse’s London-based private banking business, had a net worth in the order of “at least” $500 million between 2004 and 2008 when they were investing through Credit Suisse. Mahmoud Haji Haider Abdullah made his “business fortune” through a retail jewelry business in the 1970s and later expanding into real estate, media, telecoms, financial services, energy, oil and gas, among other things, the verdict said